The present invention relates to underwater diving with cylinders.
A diver wearing diving equipment with cylinders who has descended to around several tens of meters under the water surface must respect an ascent profile, i,e., limit his average ascent rate. In fact, during the descent, the increasing pressure causes an increasing dissolution of the gas breathed in the tissues irrigated by the blood, i.e., a storage that increases with depth and duration.
During the ascent, the ambient pressure will obviously decrease and the opposite phenomenon will take place. If this ascent is too fast, the desaturation of the gas dissolved in the tissues causes the formation of bubbles. If these come to represent a significant volume they may cause serious disorders and even lesions as they represent an additional volume which will compress the neighboring tissues. The limbs, lungs and even the central nervous system may be affected. The obstruction of the blood vessels by bubbles at the venous or arterial level leads to more serious outcomes.
Typically, a diver wears around his wrist a computer which calculates, during the ascent, an integral of the duration and depth of a dive for reading a previously-stored ascent table which displays the duration to respect for a sequence of decompression stops at staged depths.
The computer manufacturer establishes the ascent time profile table based on an algorithm from modelization of a pattern of gaseous exchanges within the tissues. This algorithm is built based on theoretical and experimental data, i.e., physical, physiological and biological data.
However, it turns out that many diving accidents still occur even when the diver has respected the decompression table. In fact, the individual susceptibility of every diver, particularly his physical condition on the day of the dive, constitutes a significant uncertainty factor as to the validity of the table.